Analysis of ISP one click download principle in stm32

If our development board doesn't have a one click download circuit , When we download the program, we should put boot 0 The jump from GND Become connected VCC, Then download , Press the reset button once to burn the program , Finally, connect VCC Become connected GND, And press reset again , In this way, the single chip microcomputer can run the program , Every burning procedure is troublesome . And when our MCU has a one click download circuit , There is no need to change boot 0 Value , Direct burning can run . Let me analyze the one click download circuit .

• Three working modes

BOOT 0	BOOT 1	Starting mode
0	X	Inside FLASH
1	0	System memory
1	1	Inside SRAM

 

 

 

 

 

• ISP One click download circuit

The picture above 1 It's the punctual atomic elite version ISP One click download schematic , chart 2 yes  mcuisp Burn Software . Look at the picture first 2 The serial number I circled in 1 The content in ,DTR Is a low level ,RTS Is a high level . Find the figure again 1 Corresponding point in DTR# and RTS#, there DTR# and RTS# Indicates the meaning of the reverse sign . Because of our mcuisp The software uses 232 Standard level , And MCU is ttl level , Their levels are opposite . So in the schematic diagram DTR There's a... In the back # It means that we CH340G The chip receives DTR Is a high level （ The serial number circled with me 1 Medium DTR The low level is opposite, so it is high level ）. Is not to say that CH340G The chip will perform logical non operations , Just a reminder sign .

• One click download process

First , Look at the serial number I circled 1,mcuisp control DTR Output low level , be DTR_N  High output , then RTS Set high , be RTS_N Low output , In this way, the triode in the schematic diagram Q3 It turns on ,BOOT 0 Be pulled high , At this time, the triode Q2 It will also turn on ,STM32F1 The reset foot of the is pulled down , That is to realize the setting BOOT 0 Automatically for 1, And press the reset key . The MCU will restart and enter ISP Pattern （ That is, system memory mode ）. Get into ISP After the model , Will lock BOOT 0 Value （ by 1）. Look at the serial number I circled 2 There is a message in , When we click start programming ,mcuisp This software is delaying 100ms Then it will automatically order DTR Increase , Release reset ,RTS Keep the high level unchanged . That is to say, it will make BOOT 0 and RESET Return to the original state . When the program is downloaded , The program has been downloaded internally FLASH 了 , You need to press reset to run the program , If you don't want to press the reset key manually , Then you can check the serial number I circled 3, In this way, the MCU will automatically reset and run .

• summary

1. To configure BOOT by ISP Pattern ,BOOT 1 The hardware is fixed as GND.Q3 Conduction ,BOOT 0 To high level .Q2 Conduction , Single chip reset .
2. Get into ISP After the model ,BOOT 0 and RESET Return to the original state .
3. ISP The download , The program runs automatically .